Speed control and synchronizing device



Aug; 29, 1944. w MYDANs 2,357,055

SPEED CONTROL AND SYNCHRONIZING DEVICE Filed Aug. 18, 1941 Z AlPLIF 5%? l m /z YIMQNDDELAY SPEED ENGINE.

CHANGE IMPULSING DEV ICE i 5 i 9 MASTER [4 7 L MOTOR Patented Aug. 29 1944 UNITED STATES PATENT orrlcs SPEED CONTROL AND BYNCHRONIZING DEVICE William E. Mydans, Cambridge, Mass. Application august is, 1941, Serial No. 401,341

'2 Claims. (cl. 115-355) This invention relates to speed control and synchronizing devices and more particularly to such devices in which two ormore rotating or moving bodies may have their speeds synchro nized either with each other or with an independent and controllable frequency device.

Synchronization of rotary elements has application to a wide variety of systems in which two or more speeds are to be compared and controlled in accordance with deviations between them. One of the important applications of such synchronization is in connection with airplane motors.

In multi-motor airplanes it is important that close synchronization of the rotational speeds of the several engines be achieved in order to secure uniform propulsion. Such synchronization also eliminates interfering vibrations which may set up beats" which may mechanically overstress structural parts of the plane and lead to the failure of such parts.

An object of this invention is to devise an arrangement whereby the several engine or motor speeds of a multi-motor plane may be synchronized within close limits to the speed of one motor selected as a master-motor" or in which all motors may be synchronized to a fixed and controllable independent frequency generated by any suitable mechanical or electrical means.

Another object of this invention is to achieve synchronization of two or more independent velocities or frequencies of movement by matchdriven directly or through a speed change device 4. If the device 4 is a step-up arrangement, the sensitivity of the system is increased. The disc, i has one or more slots or apertures I therein. On one side of the disc are two photoelectric tubes 6, I. These photoelectric tubes are located in a position so that the slot 5 travels by them during each rotation of disc I.

On the opposite side of the disc I, from the photoelectric tubes 0, I, is located a lamp 0, or other suitable source of light which is interrupted at a regular and controllable frequency. The

- lamp 8 may be a gas filled tube supplied with ing them with a frequency of movement, the

magnitude of which may be fixed or controlled, such matching means being actuated through light beams and a stroboscope device so arranged that one or the other of two photoelectric cells, but not both, are actuated according to whether the velocity of the body being controlled needs to be accelerated or decelerated.

A further. object of this invention is to ,devise arrangements of the forgoin types which are simple, reliable and flexible in their operation.

The foregoing and other objects of this invention will be best understood from the following description of an exemplification thereof, reference being had to the accompanying drawing wherein:

Fig. 1 is a diagrammatic representation of a system incorporating my invention, and; I

Fig. 2 is a diagrammatic side view of a portion of the arrangement shown in Fig. 1.

In the system illustrated, a disc i is driven by means of a shaft 2 from a rotating member such as an airplane engine 1. The shaft 2 may be electrical impulses from a suitable impulsing device ill. Each of such impulses is sufiloient to cause the lamp 8 to emit a strong dash of light throughout the duration of each ofsaid impulses. Other types of interrupted light sources might be used, such as an incandescent lamp or are, from which the light is interrupted by passage through a slot or slots in a disc rotating at a controllable speed between the light and the rotating disc i. It is desirable that the characteristics of the interrupted light source be such that the transition from light to dark be relatively sharp. Gas lamps such as 5 can be constructed with substantially no time lag so that the flashes of light emitted therefrom may have the desired sharp characteristic.

These flashes of light may be directed toward thephotoelectric tubes 6, 1 by means of a refiector 9. The impulsing device it may be adjusted to determine accurately" the number of flashes per unit time emitted from the lamp l. For example, said impulsing device ll might be an independent oscillator or a generator driven from a master motor Ii with which the engine I is to be synchronized. The motor ii might be one of the engines of the airplane or a pilot motor controlling the speeds of all the airplane engines.

l'he phot'otubes 6 and l are connected to a suitable amplifier and time delay device ll. Thus, when either one of said photo tubes is illuminated, the electrical impulse created is fed to the device i2 and amplified. This amplified impulse causes the device it to deliver at its output terminals a pulse of current which persists for a definite and pre-determined length of time, depending upon whether the photo tube 1 or 6 is illuminated. Such a pulse of current .will be delivered either to the energizing coil I! of a relay it or to the energizing coil ll of a relay ii. The period of duration of such energizing impulse may be accurately fixed at any suitable magnitude, e. g. from 0.01 to 1.0 seconds. In ei'fect, the time delay device II is such that when actuated by an impulse from one or the other of the photo tubes, it immediately closes thecircuittothe coil IIorcoil llandthatcircuit remains closed for a flxed and preferably adjustable interval of time. An adiustable member I! may be provided on the device I! in order to select any desired time interval.

After the expiration of said time interval the coils II and II are de-energlzed and the device I! becomes inoperative until the next photoelectric impulse again actuates one of the relays II or II.

The time delay section of the device I! may be oi any well known type, such as magnetic build-up-decay devices, circuits for charging and discharging condensers through fixed or variable resistors, or other well known time delay circuits. As already indicated, such devices may be readily adjusted to give a time interval at any desired value within the operating limits of the device. By varying the magnitude of this time interval, a ready means is available for altering the sensitivity of the entire system.

The relays i4 and II are provided with back contact members I1 and II respectively interposed in the circuit of the photo-cell corresponding to the opposite relay. In other words, when photo tube I energizes relay II, the back contact II de-energizes the photo tube I for the predetermined time interval mentioned above. The relay II is provided with a pair of. contact members I9 and while the relay II is provided with a similar pair of contact members 2i and 22. When the relay II is energized, its contact members I! and 20 complete a circuit from terminal II and 24 to an auxiliary motor II which operates upon a speed control device II. The motor II may be either of the rotating, solenoid or other suitable type, while the speed control device 26 may be a propeller pitch-changing means, an engine throttle or other means for altering the engine speed so as to bring it into synchronism with the frequency oi flashing of the lamp I.

The terminals 23 and 24 are adapted to be energized from a suitable source of direct current so that when the relay II closes the circuit, the motor 2I operates in a predetermined direction. This operation continues throughout the time the relay II is closed and throughout said period the speed control device acts upon the engine I so as to change its speed in accordance with the requirements of the system. Likewise the relay II, by its contact members 2i and 22, reverses the connection between the terminals 23 and 24 and the motor 2I so that upon energization of said relay II the motor II operates in the reverse direction throughout the pre-deterinined time interval and causes the speed device control II to operate on the engine I so as to change its speed in the opposite sense.

If the number of flashes per minute from the lampIisequaltotheR.P.M.oi'thedisc I,the orientation of the aperture I each time a flash of light is emitted from the lamp I will remain flxed with respect to the photo tubes I, I. The operation of the system is such that under the synchronized conditions, the lamp I will flash either before or after the slot I has passed the photo tubes I, I.

Assuming that the disc I is driven in a clockwise direction, and the speed of the disc in R. P. M. exceeds the frequency per minute of the light flashes by one B. P. M, then the posiflon of the slot I with respect to the photo cells when the light I flashes will progress in a clock-wise direction one complete revolution in one minute. Conversely, if the R. P. M. of the disc I is less than the number oi flashes of light per minute, then the position of the slot I with respect to the photo tubes when the light I'flashes will regress in a counter-clockwise direction.

IftheengineIisru ningfoofast,acondition will occur in which the slot I will uncover the tube I exactly at a time when the lamp I emits aflashof ight. Thusthetube Iwillbeilhimb nated, causing the relay II to be energized for a pre-determined interval of time, as described above. During this interval, the motor II causes the speed control device II to slow down the engine I, thus tending to bring said engine speed into synchronism with the rate of flaslnng oi the lamp I.

Normally, the interval required to change the speed of the engine I appreciably is large with respect to the time of a single rotation oi the disc I. Therefore, during the period in which the speed of the engine I is being lowered, the lighted position of the aperture I will still be progressing in a clockwise direction so as to subsequently uncover the tube I. However, since the relay II deenergizes the circuit oi the tube I throushout this interval of time, the fact that the aperture 5 permits a flash of light to fall upon the tube I will not actuate the relay II. Therefore, the system is permitted to operate in the desired direction for the requisite period or time to produce a substantial change in the engine speed without an inadvertent operation of the opposite relay.

If the control exercised by one actuation of the relay II is insufllcient to produce synchronism, the aperture I will again progress so as to permit a flash of light to fall upon the tube I. This will produce an additional slowing down of the engine 3 until proper synchronism is obtained.

1!, however, the engine I is running too slowly, the lighted position of the aperture I will regress in a counterclockwise direction and thus a flash of light will fall upon the tube I before any light is permitted to fall upon the tube I. Under these conditions the relay II will be energized producing a reverse operation of the motor II tending to increase the speed of the engine I during the pre-determined period of time, Also, the tube I will be deenergized for the purpose described above in connection with the de-energization of the tube I. Such operation is repeated until the speed of the engine I is increased sufllciently to attain synchronism.

A simple case is that in which it is desired to control closely the operating speed of a single engine at e. g. 3600 R. P. M. The lamp I is set to flash 3600 times per minute. The disc I is driven by the engine I at a one to one speed ratio. The engine may be brought approximately to 3600 R. P. M. by any suitable means, such as a tachometer and the control device is then turned on. If the lack of synchronism is great, the frequency of corrective impulses supplied to one or the other of the control relays will be so great as to be virtually continuous until a close approach to synchronism is reached. Thereupon the operation of the system will continue as described above until exact synchronism is secured. If, for example, two or more engines are to be synchronized, this may be accomplished according to this invention in various ways. For celerating means and each of said light responexample, each engine may be provided with the sive speed control devices for causing acceleracontrol system as illustrated in Fig. 1. However. tion of said member to be synchronized upon all of the flashing lamps I should be actuated light activation of one of the light responsive at an identical frequency as by being supplied I devices, and deceleration of said member to be from the same impulsing device l0. If desired, synchronized upon light activation of the other all of the discs I together with their control syslight responsive speed control device whereby the tems may be located before a single flashing lamp. rotation of said shutter member, with relation to Under these conditions all of the engines will be said pulsating light source causes a stroboscopic r ht into synchronism with the frequency of light beam to progressively move in either direct e flas ing light and thus into exact synchrotion toward one or the other of the light responnism with each other. sive devices to activate the same, depending upon Of course, this invention is not limited to the the relative rotative velocity of the shutter and particular details described above, as many equivthe pulsation frequency of the light from the light alents will suggest themselves to those skilled in source. the art. For example, the tubes 6 and 1 may be 2. In a stroboscopic speed synchronizing apof the photo-cell barrier type ,or other suitable paratus, for regulating the speed of a member light responsive im Also, in t n to the to be controlled, a. rotary shutter driven by said adjustments for altering the sensitiv y of the y member to be controlled at a fixed speed ratio tern described above, additional means for such .40 thereto, said shutter having a light-passing aper- P e m y be tilized. For example, the size ture therein radially spaced from the axis of ro- Of the aperture 5 y b Vefled- A180. a p tation of the shutter, a pair of light-sensitive ralitv of such pe e m y be p o i e t e speed-control devices fixed in side-by-side relalneleasing e number 01 light i p t tion adjacent one side of the shutter at substanmitted through the disc I during each unit of tlally equally spaced distances from the shutter, time- Likewise, t e p 8 m t be d t and at a radial distance from the axis of the shutflash at frequencies higher o t at 8 ter equal to the distance between the rotary axis fix whole i t r-r t o with r sp ct to the r iof the shutter and the center of the aperture eren e pe t which it i e ired to syn hron z in the shutter, speed accelerating and deceleratthe Speed 01 n i 3- Ot e V i s and ing means for controlling the speed of the memadaptations utilizing the present invention will her to be synchronized, and an operating connecly suggest m v I i rdi ly tion between each of said light-responsive s eedir h t t e pp nd l m b iven a ro control devices and said speed accelerating and interpretation su te w t t scope of decelerating means for causing acceleration or t e nve i W t the rt. said member to be controlled upon activation of What is claimed is: one of the light-responsive devices, and decelera- In a StIObOSOODiO p e Syn r 4 tion of said member to be controlled upon light D Speed determining ns omprising 8- activation of the other light-responsive speedpulsating light o r e h ving me ns r causing control device, a pulsationg light source located said light pulsations to occur at a predetermined i0 adjac nt the shutter, equidistant from the two substantially uniform recurrent reference speed li ht-sensiti e speed-control devices and at a determining frequencies, a pair of light responsive radial distance from the rotary axis of the shutspeed control devices arranged to receive light t r substantially equal to the distance between from the light source, and located in adjacent th tt a n t t ir t h tt r a rrelation, a rotating member to be synchronized, ture, said pulsating light source h vi l e a rotary shutter member driven by said rotating r icausing said light pulsations tooccur at premember in a fixed speed ratio thereto, positioned determined substantially uniform recurrent reft in r p e passa f light between said erence s eed determining frequencies whereby the l h source and both 1 id light resp n iv rotation of the shutter member, with relation to speed control devices, said shutter having a light the pulsating light source causes" a stroboscopic passing opening therein movable with the shutter l t b a to progressively move in either diree member to p fl e v y p e e light source tion toward one or theother of the light-responto each 01 said liflht responsive speed control sive devices to activate the same, depending upon vi s du n a p rt n o a h tat o the the relative rotative velocity of the shutter and s t me e sp ed ce e i and d the ulsation frequency of the light from the light erating. means for controlling the speed of said some, member to be synchronized and an operating con- WILLIAM E. M nection between said speed accelerating and de- 

